Not to hijack Laura's thread on light therapy, but she mentioned the pineal gland. A quick search on the pineal gland reveals that it is highly susceptible to flouride accumulation....in almost all public water supplies in the US.

Here's a youtube video about this:

http://www.youtube.com/watch?v=XSZQ3ixu7a4

and an article discussing the researcher discovering the relationship between flouride and the pineal gland:

http://www.fluoridealert.org/issues/.../pineal-gland/

There are many articles about how to "clean up" your pineal gland so I won't post all those links here.

Just wanted to note that as Rick has pointed out the importance of the Industrial Revolution, perhaps we should also be looking at the PD rate when our water supplies began being flouridated. BTW, many cities, including the very first city in the US to flouridate its public water supply, are now seeking to de-flouridate them. We are finally realizing what a horrendous idea that is.